论文标题

掩盖随机扰动的晶格的基础远程顺序

Cloaking the Underlying Long-Range Order of Randomly Perturbed Lattices

论文作者

Klatt, Michael A., Kim, Jaeuk, Torquato, Salvatore

论文摘要

晶格上颗粒的随机,不相关的位移可保留原始晶格的过度均匀性,即在无限波长的极限中消失的归一化密度波动消失。除了弥漫性贡献外,来自结果点模式的散射强度通常还继承原始晶格的Bragg峰(远程顺序)。在这里,我们演示了如何以独立和相同分布的扰动的有效衍射模式隐藏这些bragg峰。当且仅当移动晶格点位置的所有概率密度之和的总和在所有位置上都是常数时,所有Bragg峰都消失了。然后,基本的远程顺序被“掩盖”,因为它不能单独从配对相关函数中重建它。一方面,密度波动随着扰动$ a $的强度而单调增加,这是由超均匀度订单$ \overlineλ$衡量的。另一方面,远程顺序的消失和重新出现,具体取决于系统是否被掩盖,随着扰动强度的增加,$τ$订单度量明显捕获。因此,尽管对于扰动晶格的订单度量标准,$τ$订单度量是一个较高的选择,但摄入强度$ a $似乎是自然的选择。值得注意的是,被遮挡的扰动晶格可以轻松模拟无序的无均匀点模式(至少$ 10^6 $颗粒),而没有bragg峰。

Random, uncorrelated displacements of particles on a lattice preserve the hyperuniformity of the original lattice, that is, normalized density fluctuations vanish in the limit of infinite wavelengths. In addition to a diffuse contribution, the scattering intensity from the the resulting point pattern typically inherits the Bragg peaks (long-range order) of the original lattice. Here we demonstrate how these Bragg peaks can be hidden in the effective diffraction pattern of independent and identically distributed perturbations. All Bragg peaks vanish if and only if the sum of all probability densities of the positions of the shifted lattice points is a constant at all positions. The underlying long-range order is then 'cloaked' in the sense that it cannot be reconstructed from the pair correlation function alone. On the one hand, density fluctuations increase monotonically with the strength of perturbations $a$, as measured by the hyperuniformity order metric $\overlineΛ$. On the other hand, the disappearance and reemergence of long-range order, depending on whether the system is cloaked or not as the perturbation strength increases, is manifestly captured by the $τ$ order metric. Therefore, while the perturbation strength $a$ may seem to be a natural choice for an order metric of perturbed lattices, the $τ$ order metric is a superior choice. It is noteworthy that cloaked perturbed lattices allow one to easily simulate very large samples (with at least $10^6$ particles) of disordered hyperuniform point patterns without Bragg peaks.

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